When Enik walks out of the Marshalls' cave at the end of the episode, you can see his shadow on what is supposed to be the sky (but is really just a blue backdrop)
This episode marks the first time that any of the Marshalls had a real opportunity to get home. During Will's quest to gain Enik's help for Rick, Enik opens the time doorway. It stops briefly at Earth, and Enik urges Will to cross through. Will wants to, but refuses to leave his family behind. Enik has to stay as well, because it is his law that no other can offer a greater sacrifice than an Altrusian.
We learn that red and yellow crystals create a small explosive flash; red and blue combined with a yellow result in a severe, paralyzing shock.